Wellness . Symptoms guide
Brain Fog: Hormonal and Nutritional Causes
Brain fog is a real symptom with many medical drivers. Among the most common reversible causes are thyroid dysfunction, iron deficiency, B12 deficiency, vitamin D deficiency, perimenopause and low testosterone in men. A combined panel covers all of these in one appointment.
This patient information is being clinically reviewed by our team. The factual content draws on UK guidance (NHS, NICE, British Association of Dermatologists, British Society for Sexual Medicine where cited).
What this might be
- Thyroid dysfunction. Both hypo and hyper can blur concentration.
- Iron deficiency. Even without anaemia, low ferritin impairs cognitive function.
- B12 deficiency. Direct effect on neural function.
- Perimenopause and menopause. Oestrogen change affects cognition.
- Low testosterone in men. Often presents with fatigue and brain fog together.
- Sleep apnoea. A clinical referral is appropriate when suspected; bloodwork rules out the reversible biochemistry first.
Common features that suggest this
- Difficulty concentrating
- Word-finding problems
- Mental fatigue out of proportion to activity
- Memory lapses
- Persistent for 4 or more weeks
Recommended tests
Same-day appointments at our Harley Street clinic, results clinician-reviewed.
Need a marker not in these panels? Build a custom panel and a GMC-registered clinician will design one for you.
Testing advice
Morning appointment. No fasting needed for hair or hormone panels; fasting preferred for General Wellness.
Common questions
Is brain fog real or in my head?
It is real and measurable in many conditions. Calling it brain fog is just the descriptive label; the medical drivers are clearly identifiable on bloodwork in many cases.